JOURNAL OF CONCHOLOGY. 42 1 



this may go on for several months of the year only, in our canal 

 at Armley probably all the year round. The following focts 

 support this view. No gill pouches of SphcBriuni corjieuin that 

 I have examined possessed young with shells of equal size; the 

 brood pouches could not have retained the number of indi- 

 viduals they actually did possess if these had grown equally, for 

 the gill tissues are merely held by concrescence, and are separ- 

 ated by the larger forms as they grow ; the young of Sphcerium 

 spins a byssus, probably to retain it in the brood pouch whilst 

 the larger forms are passing out ; embryos of all sizes are to be 

 found at one time in a brood pouch. These little embryos are 

 most exquisite objects for the microscope— the tiny shells, the 

 crawhng ciliated foot, the paired otocysts with the pulsating 

 otohths at one end of the capsule, each with a little streak, like 

 a crease in a minute air-bubble, the tuft of tinted liver caec^, 

 and a heart pulsating at sixty beats per minute. These and many 

 other points might be profitably enlarged upon did space per- 

 mit, many structures I have passed over for this reason. No 

 animal offers easier study of cell structure. The blood cor- 

 puscles are best procured from a teased bit of mantle. The 

 shell is covered with a brown periostracum, which is hairy, the 

 hairs being simple and curved. 



Amongst the parasites and commensals, I have noticed the 



young of the river leech, intestinal worms, Cyclops, Vorticella, 



. Stentor, Parainaciuni, and Amczha, some of the temporarily 



fixed Protozoa being attached to the base of the foot and 



others bejewelling the shells. 



♦-•♦•♦ 



On Gibbula incincta Sowerby. — In looking over the 

 last Journal, I see a description by Mr. Sowerby of a Gibbula 

 mciuda, from Port Elizabeth. This seems to me to be the 

 same as my Gibbula tryo?ii {^Mdcn. Conch.,' xi., p. 239, pi. 57, 

 figs. 20-21, 1889), although my shells are larger. Perhaps, if 

 you will publish this note, someone may compare Mr. Sowerby's 

 (unfigured) specimens with my figures and description, and so 

 decide the question. — H. A. Pilsbry, Philadelphia, U.S.A. 



